The intrinsic circuitry in the olfactory bulb is designed to shape incoming odorant information via a highly specialized inhibitory network. The unique physiology and morphology of the principal neurons in the bulb suggest that attributes of local circuits and intrinsic conductances underlie the initial processing of olfactory information. The flow of olfactory information begins with the interaction of odorant molecules with odorant receptors in the nasal epithelium. The resultant sensory information is mapped onto the main olfactory bulb via the axons of olfactory receptor neurons. Mitral cells and tufted cells, the principal neurons of the bulb, receive input from olfactory receptor neurons in a complex synaptic structure called a glomerulus. Dendrodendritic synapses between principal cells and intemeurons mediate the inhibitory activity in the bulb. The output of the olfactory bulb is governed by the interaction of these inhibitory synaptic potentials with the intrinsic conductances of principal cell processes. The predominance of dendrodendritic synapses in bulb circuitry puts a premium on an understanding of dendritic processing. Here, we propose to investigate two aspects of dendritic processing, autoexcitation and the conductance of potentials in dendrites. Whole-cell patch clamp measurements will be made from visually identified mitral and granule cells. We will also use paired somatic and dendritic and direct dendritic recordings from mitral cell primary and secondary dendrites. The specific aims are: (1) to determine the function of autoexcitation in mitral cell processing and (2) to determine how dendritic compartmentalization effects mitral cell processing.